用作核磁共振发射线圈的高温超导谐振器的时域和频域响应
Time and Frequency Domain Response of HTS Resonators for Use as NMR Transmit Coils.
作者信息
Amouzandeh Ghoncheh, Ramaswamy Vijaykumar, Freytag Nicolas, Edison Arthur S, Hornak Lawrence A, Brey William W
机构信息
National High Magnetic Laboratory and the Department of Physics, Florida State University, Tallahassee, FL 32310 USA.
Bruker Biospin AG, Faellanden 8117, Switzerland.
出版信息
IEEE Trans Appl Supercond. 2019 Aug;29(5). doi: 10.1109/TASC.2019.2902522. Epub 2019 Mar 4.
Replacing normal metal NMR coils with thin-film high-temperature superconductor (HTS) resonators can significantly improve the sensitivity of analytical NMR. To study the use of these resonators for excitation as well as detection, we investigated the radio frequency properties of the HTS NMR coils in both frequency and time domain at a variety of transmit power levels. Experiments were conducted on a double-sided, counter wound spiral resonator designed to detect NMR signals from C nuclei at 14.1 T. Power-dependent nonlinearity was observed in the transmission coefficient and quality factor. The ability of the HTS resonators to accurately generate short pulses was studied in the time domain over the range power levels. The results of this study show that some form of Q switching is needed to get good transmit performance from HTS coils for C. For that purpose, the effect of adding a shorted transmission line stub to improve the pulse shapes and reduce phase transients was studied.
用薄膜高温超导（HTS）谐振器取代普通金属核磁共振线圈可显著提高分析核磁共振的灵敏度。为研究这些谐振器用于激发和检测的情况，我们在多种发射功率水平下，在频域和时域研究了高温超导核磁共振线圈的射频特性。实验是在一个双面、反向缠绕的螺旋谐振器上进行的，该谐振器旨在检测14.1 T下碳核的核磁共振信号。在传输系数和品质因数中观察到了功率相关的非线性。在时域中研究了高温超导谐振器在不同功率水平范围内精确产生短脉冲的能力。这项研究的结果表明，需要某种形式的Q开关才能使高温超导碳线圈获得良好的发射性能。为此，研究了添加短路传输线短截线对改善脉冲形状和减少相位瞬变的影响。
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